Flexible joints

Claim 1

In a protective suit subjected to an internal/external pressure differential, a flexible joint having passage means therethrough for the reception of a human limb, said flexible joint comprising an annular male member movably housed within an annular female member, said male member at least in part defining an annular part-spherical piston having radially displaced inner and outer walls and a head, said female member at least in part defining a part-spherical closed annular cylinder defined by spaced inner and outer walls with one end of said cylinder being open and receiving said piston for angular movement within said cylinder, the spacing of said cylinder inner and outer walls being greater than the spacing of said piston inner and outer walls with there being a positive clearance between respective walls of said piston and cylinder, a sealing liquid within said cylinder in direct contact with said piston and surrounding said piston head and that portion of said piston inner and outer walls disposed within said cylinder, and fixed narrow annular inner and outer sealing ring means carried on said cylinder inner and outer walls adjacent said open end and slidably engaging said piston walls with said inner and outer cylinder walls being subjected to the pressure of said sealing liquid in all positions of said piston, said piston and said cylinder having a common centre of rotation, said inner and outer sealing ring means lying in a plane extending generally through said common centre, the initial relative positions of said piston and said cylinder and the depth of said cylinder being one wherein when said piston is moved to an angular position relative to said cylinder said piston head engages said cylinder closed end prior to a diametrical opposed portion of said piston moving out from between said inner and outer sealing ring means thereby maintaining said piston within said cylinder and the seals between said piston and said cylinder.